Fiber Fuzzing of Prepreg

Fiber fuzzing on the prepreg surface affects lay-up. When glass fibers are exposed, the product surface appears white or grayish-white hazy, feels rough to the touch, and is most conspicuous on dark-colored products. This is because the surface resin fails to fully encapsulate the glass fibers, and the fibers are directly exposed. Abnormal glass fiber orientation manifests macroscopically as different shrinkage rates in various directions, causing unpredictable warpage deformation of the product. Fiber-related defects are especially critical in structural parts because fiber distribution and orientation directly affect the strength and stiffness of the product.

1. Process parameter factors: fiber tension fluctuations, rough surface of the dipping roller, wear of fiber yarn guides, and excessive prepreg manufacturing speed. 2. Preheating factors: The preheating temperature and time of the material (especially thermosetting molding compounds) directly affect its fluidity and curing behavior; improper preheating leads to poor filling or uneven curing, and is a key control point unique to compression molding. 3. Molding pressure factors: In compression molding, pressure is not only used to overcome flow resistance, but also directly affects the compactness of the product and the degree of fiber wetting; insufficient pressure is an important cause of loose products and insufficient strength.

1. Process parameter optimization and adjustment: Stabilize fiber tension, polish the dipping roller, replace worn yarn guides, and control the manufacturing speed. 2. Systematic troubleshooting method: Troubleshooting of compression molding problems follows the order of "material -> temperature -> pressure -> mold". First check the preheating and fluidity of the material, then verify the mold temperature distribution and curing time, then adjust the molding pressure and mold closing speed, and finally check the mold venting and demolding conditions. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points.

This problem is a typical manifestation of fiber fuzzing of prepreg in compression molding. The core of the solution lies in the reasonable preheating of the material and the guarantee of fluidity, as well as the precise matching of mold temperature and molding pressure. It is recommended to make coordinated adjustments from both the material state and process parameters.